24.[Leetcode]Swap Nodes in Pairs

题意:

交换相邻（adjacent）的节点

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我的思路;

//c++ recursive，效率是不高但是比较短class Solution {public:    ListNode* swapPairs(ListNode* head) {        if(!head || !(head->next)) return head;        ListNode *c = head, *n = head->next, *f = head->next->next;        n->next = c;        c->next = swapPairs(f);        return n;    }};